To better enjoy the benefit of f

To better enjoy the benefit of free flow of goods, services, capital, labor and other resources，countries have signed various agreements to liberalize trade among themselves while possibly ______ barriers to economic activities with non-members.
A、putting up
B、put up
C、putted up
D、following up
【正确答案】：A
【题目解析】：To better enjoy the benefit of free flow of goods, services, capital, labor and other resources，countries have signed various agreements to liberalize trade among themselves while possibly putting up barriers to economic activities with non-members.参见教材P35。